Alkylation process



Feh s, 1958 M. KNIGHT ETAL ALKYLATION PROCESS Filed July 6, 1956INVENTO/YS Joe 7. Kelly Harmon M. [Orig/n ymz I Arm/Mfr ALKYLATIONPROCESS Harmon M. Knight, La Marque, and .loe T. Kelly, Dickinson, Tex.,assignors to The American Oil Company, Texas City, Tern, a corporationof Texas Application July 6, 1956, Serial No. %,341

9 Claims. (Cl. 260-683.44)

This invention relates to the reaction of isoparafiins or aromatichydrocarbons and olefins. More particularly it relates to the alkylationof isobutane with ethylene.

In the petroleum industry today, the octane race has placed a strain onfacilities and materials needed to make gasoline meeting present dayautomotive engine require ments. One of the remaining sources of highoctane components is the product of the alkylation of isobutane andethylene. This alkylation is not easy to carry out, particularly on alarge scale.

An object of the invention is parafiins, particularly isobutane, larlyethylene. Another object is the alkylation of aromatic hydrocarbons witholefins. Other objects will become apparent in the course of thedetailed description.

the alkylation of iso- With olefins, particu- The alkylation ofisoparaffins or aromatic hydrocarbons with olefins is carried out in thepresence of a novel catalyst pair. One member of the catalyst pair isboron trifiuoride. The other member of the catalyst pair isphosphomolybdic acid containing water of hydration, hereinafter spokenof as a hydrate. Although the second component of the catalyst pair isspoken of as a hydrate, it is believed that the solid member is moreproperly a complex of the phosphomolybdic acid hydrate and E1 the B1 isbelieved to complex with some or all of the hydrate water present inphosphomolybdic acid. More than the amount of BF needed to complex withthe water of hydration is necessary to obtain the desired catalyticeffect.

Boron trifluoride is one member of the catalyst pair. Commercial gradeanhydrous boron trifiuoride is suitable for use as one member of thecatalyst pair.

It is necessary that the phosphomolybdic acid contain hydrate water. Theanhydrous acid does not have any promotional effect on the activity ofB1 it is not necessary that any particular hydrate be used; apparentlyit is necessary only that some water of hydration be present.

The BP and the defined acid react to form a solid material containingcomplexed BFg When the hydrate and BF;., are contacted in a closedvessel, the BE, partial pressure drops very rapidly at first and thengradually approaches a constant value. It appears that a very rapidreaction between the BP and some of the water of hydra tion takes place.This initially rapid reaction is then followed by a relatively slowreaction between the remaining molecules of hydrate water and additional8P It appears that when the hydrate is exposed to BFg, even in thepresence of hydrocarbon reactants, eventually all of the water ofhydration will become associated with BT on about a 1 mole of 131 permole of hydrate water basis. A complex of the defined hydrate and B1 isnot an effective catalyst for the alkylation in the absence of free-B1Free-BF, is to be understood as BF existing in the reaction zone whichis not complexed with the defined hydrate. As soon as the hydrate hascomplexed with some BF the beneficial catalytic effect exists. Thusfree-B1 may exist inthe reaction zone, as evidenced by" the formationof'alkylate, even though all of the hydrate water has not beencomplexed. In a batch system,

2,824,162 Patented F eb. 18, 1958 "ice wherein less BF is present thanis theoretically required to complex all the water of hydration presentin the hydrate, eventually no alkylation will occur as charge is added,since all of the BF will become complexed.

In general, the process is carried out utilizing an amount of BF whichis in excess of that required to complex with all the hydrate waterpresent in the contacting zone, namely, in excess of about 1 mole of B1per mole of hydrate water present. More than the minimum amount offree-3P is beneficial, in fact, the yield of alkylate increases rapidlywith increase in free-BF present, up to a maximum amount. The amount offree-BF used is dependent somewhat upon the reactants themselves.However, when reacting isoparaffins and olefins, the free-B1 usage isdesirably, set out on a BF to olefin weight ratio, of at least about0.2. In other words, at least about 0.2 lb. of free-BF per lb. of olefincharged to the alkylation zone is desirable. About 1.5 parts by weightof B1 per part of olefin charged appears to be about the desirablemaximum usage of B1 It is preferred to use between about 0.35 and 1 partby weight of free-B1 per part by weight of olefin when utilizing thelower molecular weight olefin, such as ethylene and propylene.

The process may be carried out at any temperature below the temperatureat which the hydrate decomposes, that is, loss of all its water ofhydration. The temperatures of operation may be as low as C. or evenlower. Temperatures as high as 150 C. and even higher may be used;however, more usually the temperature of operation will be between about0 C. and 100 C. Lower temperatures appear to favor the formation of thehydrocarbons having 6 to 7 carbon atoms. It is preferred to operate at atemperature between about C. and C.

Sufficient pressure is maintained on the system to keep a substantialportion of the hydrocarbons charged in the liquid state. The process maybe carried out at relatively low pressures, for example, p. s. i., or itmay be carried out at elevated pressures, for example, 2000 p. s. i. ormore. In general, pressures will be between about 200 and 1000 p. s. i.,and preferably between about 300 and 600 p. s. i.

The contacting of the isoparaffin or aromatic hydro carbon and theolefin in the presence of the defined catalyst pair is continued untilan appreciable amount of alkylate has been formed. In batch reactions,it is possible to virtually extinguish the olefin, i. e., convertessentially 100% of the olefin by a sufiiciently long period ofcontacting. When operating in a continuous flow system, it may bedesirable to have a time of contacting such that substantial amounts ofolefin are not converted and obtain the complete conversion of theolefin by a recycle operation. The time of reaction. will be determinedby the type of hydrocarbons charged, the ratio of isoparafiin oraromatic to olefin, the degree of mixing in the contacting zone and thecatalyst usage. A few tests will enable one to determine the optimumtime of contacting for the particular system of operating conditionsbeing tried.

The reactants in the hydrocarbon charge to the alkylation process areisoparafiin, or aromatic and olefin. The olefin contains from 2 to about12 carbon atoms. Examples of suitable olefins are ethylene, propylene,butenea 2, hexene and octene; in addition to these, the olefin polymersobtained from propylene and/or butylene are also suitable for use in theprocess, such as co'dimer, propylene trimer, propylene tetramer andbutylene trimer. It is preferred to operate with ethylene or propylene.

The aromatic hydrocarbons must be alkylatable by the particular olefinused. It is self-evident that an aromatic hydrocarbon which contains.alkyl substituents positioned the possibility of alkylation with theparticular olefin should not be subjected to the process. Examples ofparticularly suitable aromatic hydrocarbons are benzene, toluene,xylene, trimethylbenzenes, and the other alkyl analogues, such as propyland butyl; the naphthalene aromatic hydrocarbons, such as the mono and(ii-substituted methylnaphthalenes.

The isoparafiin reactant is defined as a parafiinic hydrocarbon whichhas a tertiary hydrogen atom, i. e., parafilns which have a hydrogenatom attached to a tertiary carbon atom. Examples of these areisobutane, isopentz-me (LIL methylbutane), 2 methylpentane, 2methylhexane, 3- methylhexane, 2,3-dimethylbutane (di-isopropyl) and 2,4-dimethylhexane. Thus the isoparatiins usable as one reactant in theprocess contain from 4 to 8 carbon In the isoparaffin-olefin system, thealkylation reaction is more favored as the mole ratio of isoparafiin toolefin increases. In general, the isoparafiin to olefin mole ratio inthe hydrocarbon charge should be at least 1. More than this amount isgood and it is desirable to have an isoparaflin to olefin ratio betweenabout 2 and 25 and in some cases more, for example, as much as 50. It ispreferred to operate with an isoparaflin to olefin mole ratio of betweenabout 5 and 15.

The presence of non-reactive hydrocarbons in the hydrocarbon charge isnot detrimental unless the reactants become excessively diluted. Forexample, the isoparaffin may also contain isomers of the normalconfiguration. The olefin may contain parafiins of the same carbonnumber. Mixture of 2 or more isoparafiins or 2 or more aromatichydrocarbons, or 2 or more olefins may be charged. In general, when aparticular product distribution is desired, it is preferable to operatewith a single isoparafiin and a single olefin, for example, technicalgrade isobutane and ethylene, both of about 95% purity.

The reactants may be mixed together before they are charged into thereactor. Or, they may be charged into the reactor separately. Or, aportion of the olefin may be blended with the isoparafiin or aromaticbefore introduction into the reactor and the remainder of the olefininjected into the reactor. The charge may be introduced all at one pointinto the reactor or it may be introduced at 2 or more points. Thealkylation reaction is somewhat exothermic and temperature control isfacilitated by introducing the olefin into the reactor at more than onepoint.

The BF member of the catalyst pair may be premixed with the isoparah'inand olefin before introducing these into the reactor but this should notbe done when an extremely reactive system such as isobutane andisobutylene or aromatic hydrocarbons and olefin are being used; or whenan olefin that is very rapidly polymerizable is being used. The BF maybe blended with the isoparafiin reactant and introduced into the reactorwith this member when the isoparaflin and the olefins are beingintroduced separately. The BF may also be introduced directly into thereaction zone independently from the hydrocarbons charged. The BF may beintroduced into the reactor at a single point or at several points tohelp control temperature and reaction rate.

The reactor may be a vessel providing for a batch-type reaction, i. e.,one wherein the desired amount of isoparaffin or aromatic and olefin arecharged to a closed vessel containing the catalyst pair and the vesselthen maintained at the desired temperature for the desired time. At theend of this time, the hydrocarbon product mixture and unreactedmaterials are withdrawn from the vessel and processed to separate thealkylate product from the unreacted materials and lower and highermolecular weight materials. operation wherein the reactants and free-B1are flowed through the bed of the hydrate member of the catalyst pair,the space velocity being controlled so that the desired amount ofreaction is obtained during the passage of the reactants through the bedof hydrate. Under some The reactor may be a fixed bed r conditions, amoving bed of hydrate may be utilized. In still another set ofcircumstances, a fluidized bed of hydrate may be utilized with theincoming stream of reactants providing the energy for the fluidizationof the solid hydrate. Other methods of operation common in the catalyticrefining aspects of the petroleum industry utilizing solid catalyst maybe readily devised.

It has been pointed out that the solid member of the catalyst pair isreally a complex of the phosphomolybdic acid hydrat 1d BF the B1apparently reacting with the water 0 ration. The complex may bepreformed, by exposing the hydrate to SP for a time sufiicient tointroduce some BF into the solid component or even enough to complex allof the water of hydration; this 51 being done before the reactants areintroduced into the reaction zone or even before the solid member of thecatalyst pair is positioned in the reaction zone. The complex may beformed in situ during a batch-type reaction. In the batch-typeoperation, it is convenient to introduce all the BF into the reactionvessel at once. This amount of BF is sufiicient not only to complex withthe water of hydration but also provide the desired amount of free- BFIn a flow system, the solid member may be prepared in situ by chargingfresh hydrate to the reaction zone and forming the complex during theinitial passage of reactants and B1 over the hydrate. Some alkylationreaction occurs even though the hydrate has not taken up sufiicient BFto complex all the water of hydration. As the How of reactants and B1continues over the solid member, eventually the hydrate will becomesaturated with respect to 5P At this time, the amount of 8P introducedinto the reaction zone should be cut back to that amount of free-BFdesired, under this particular set of operating conditions.

The illustrative embodiment set out in the annexed figure forms a partof this specification. It is pointed out that this embodiment isschematic in nature, that many items of process equipment have beenomitted, since these may be readily added by those skilled in this artand that this embodiment is only one of many which may be devised, andthat the invention is not to be limited to this particular embodiment.In this embodiment, it is desired to produce a high yield ofdi-isopropyl for use as a blending material for gasoline. Ethylene fromsource 11 is passed by way of line 12 into mixer 13. Liquid isobutanefrom source 14 is passed by way of lines 16 and 17 into mixer 13. Boththe ethylene and the isobutane are about purity, the remainder beingn-butane and ethane, with trace amounts of other components found inmaterials derived from petroleum refining sources. Mixer 13, in thisinstance, is a simple orifice-type mixer suitable for intermingling aliquid and a gas, or two liquids. Recycle isobutane from line 18 ispassed by way of line 17 into mixer 13. In this embodiment, the molarratio of isobutane to ethylene is 6.

From mixer 13, the blend of isobutane and ethylene is passed by way ofline 19, through heat exchanger 21, where the temperature of the blendis adjusted to 30 C. The temperature of the blend leaving exchanger 21is somewhat lower than the reaction temperature, since there is a heatrise in the reactor due to exothermic reaction. From exchanger 21, thestream of isobutane and ethylene is passed by Way of lines 22 and 23into the top of reactor 24.

Boron trifluoride is passed from source 26 by way of valved line 27 andline 28 into line 23, where .it meets the stream of isobutane andethylene. If desirable, a mixer may be introduced into line 23 to insurecomplete intermingling of the BF and the hydrocarbon charged. Recycle BFis introduced from line 29 by way of lines 28 and 23. In thisembodiment, the hydrate is completely complexed with respect to BF andonly the necessary free-BF is introduced by way of line 28. The weightratio of free-BF from line 28 to ethylene present in line 23 is 1.1.

Reactor 24 is shown as a shell and tube type vessel. The hydrate iscontained in the tubes 31. The alumina balls 32 and 33 are positionedabove and below the headers in the reactor to maintain the hydratewithin the tubes. In order to maintain the temperature in the reactor atsubstantially 35 C., water is introduced into the shell side by way ofline 36 and is withdrawn by way of line 37.

In this embodiment, the reactor was charged with phosphomolybdic acidcontaining about 1 mole of water per mole of acid. The hydrate waspreformed into pellets about one-eight inch in diameter and aboutoneeighth inch in height. Some silica was present to act as a lubricantin the extrusion of the pellets. The hydrate was contacted with BF in anamount such that all of the water of hydration was complexed with BFThis operation was carried out before reactants were introduced into thereactor. The reactor pressurewas maintained at 600 p. s. i. This permitsmaintaining the isobutane and substantially all of the ethylene in theliquid state.

The product hydrocarbon mixture is passed out of reactor 24 by Way ofline 41. This stream contains the alkylate product, unreacted isobutane,a small amount of unreacted ethylene and pentanes as well as BF Thestream from line 41 is passed into gas separator 42 where the BFisobutane, some pentanes and some alkylate product are taken overhead byway of line 43. .The material taken overhead from the separator 42 ispassed into fractionator 44.

Fractionator 44 is adapted to separate the BF as a gas, the isobutane asa liquid and the higher boiling materials as a bottoms product.Fractionator 44 is provided with an internal reboiler 46 and an internalcondensor 47. BF and unreacted ethylene are taken overhead fromfractionator 44 by way of line 48 and may be passed out of the system byway of valved line 49. The material from line 49 may be periodicallypassed to a BB; purification operation to remove non-condensable inertgases which build up in the system. Ordinarily the stream from line 48is recycled by way of valved lines 29 and lines 28 and 23 to reactor 24.

Isobutane is withdrawn as a liquid stream by way of line 51 and isrecycled by way of lines 18 and 17 to mixer 13 for reuse in the process.Bottoms product from fractionator 44 is withdrawn by way of line 52 andmay be passed to storage or further processing by way of valved line 53.This stream from line 52 consists substantially of isopentane. Someunsaturated C hydrocarbons are also present and also a small amount ofhigher boiling alkylate material.

The liquids separated in gas separator 42 are passed by Way of line 56into fractionator 57. The bottoms product from fractionator 44 may bepassed by Way of valved line 58 and line 56 into fractionator 57 forcomplete removal of the alkylate material. In this embodiment, thebottoms are passed to fractionator 57.

Fractionator 57 is provided with an internal reboiler 58 and is adaptedto produce the desired alkylate products from the hydrocarbon productmixture entering from line 56. A vapor stream is taken overhead by wayof line 61, is condensed in cooler 62 and is passed to storage by way ofline 63. The material from line 63 consists substantially of isopentaneand some unsaturated C material. This material may be used as a highoctane blending stock for the production of motor gasoline of thedesired volatility characteristics.

The alkylate product herein is considered to be that boiling above thepentane range and boiling below the maximum temperature usable in motorgasoline. In general, a 415 F. endpoint alkylate is blendable into motorgasoline without adverse effect in a specification calling for a 400 F.gasoline endpoint. Thus the alkylate prodnot is considered to be thematerial boiling between about the lower limit of the hexane range and415 F. in the ASTM distillation procedure.

A considerable diiference exists between the octane number of the Cfraction of the alkylate product and the higher boiling material. The Cfraction, which boils from about 110 to 170 F., has an F-l octane numberof 101. The Cq+ material has an octane number which ranges between about75 and 85, depending somewhat on the fractionation.

Light alkylate, which includes all the C material and some of the Cmaterial, is withdrawn from fractionator 57 by way of line 66. Heavyalkylate, which includes most of the C and material boiling up to 415 F.is withdrawn from fractionator 57 by way of line 67. A small amount ofhigher boiling bottoms is withdrawn by way of line 68.

In general, the C fraction of the alkylate product will contain fromabout 86 to about 90 mole percent of diisopropyl (2,3-dimethylbutane).2-methylpentane and S-methylpentane represent substantially theremainder of the C product. Generally, only trace amounts of n-hexaneare present.

In Table I, there are set out runs carried out under what are more orless standard conditions, namely, a 4-liter carbon steel bomb was driedovernight in a stream of hot air at C. The hydrate to be tested (90grams) was charged to the bomb as a powder and the bomb was evacuated.One kilogram of a dry blend of ethylene and isobutane was added and thenBF (90 grarns) was pressured in. The charged bombs were placed in arocker and allowed to rock for 20 hours. At the end of this time aliquid sample was drawn through a bomb containing activated alumina (toremove dissolved BF and salt particles). This sample was submitted forPodbielniak distillation. A C cut from the Podbielniak distillation wasanalyzed by mass spectrometer. In some cases after sampling, theremaining major portion of the product was debutanized on an Oldershawcolumn and then fractioned on a packed column.

In run No. 1, the operation was carried out as described above exceptthat no hydrate was present in the bomb. The results show that only 34%of depentanized alkylate product was obtained by the use of B1 alone asthe catalyst. Run No. 2, carried out with phosphomolybdic acid hydrateproduced 139% alkylate. Run No. 3 shows silicomolybdic acid hydrate isineffective.

TABLE I Run No 1 2 3 Phospho- Silico Hydrate None molybclic molybdicAcid Aci Conditions:

Isobutane/Ethylene (Molar) 3. 0 2. 1 2.1 Hydrocarbon/Hydrate (Weight)10. 6 11. 2 Bi s/Ethylene (Weight) 0.7 0.6 0.6 Time, Hours 20 20 20Temperature, 0.... 25-35 20-25 25-30 Pressure (Range), p. 300 315-205328-330 Results:

Alkylate (Depentanized) 1 (wt.

percent)- Pentanes 0 17 0 Total 34 139 10 Ethylene Converted,Percent"-.- 66 81 1 Podbielniak and mass spectrometer analyses, based onethylene charged.

2 89% 2,3-dimethylbutane.

We claim:

1. An alkylation process comprising contacting (a) an alkylatable feedhydrocarbon from the class consisting of (1) isoparaffin having from 4to 8 carbon atoms and (2) aromatic hydrocarbon and (b) an olefin havingfrom 2 to 12 carbon atoms, in the presence of a catalyst comprisingessentially (i) phosphomolybdic acid containing water of hydration, and(ii) BF said BF being present in an amount in excess of about 1 mole permole of water of hydration in said acid, at a temperature between about30 C. and a temperature substantially below the temperature at whichsaid hydrate decomposes, and at a pressure suflicient to maintain asubstantial portion of said reactants in the liquid state, andseparating a hydrocarbon product mixture containing alkylate product ofsaid feed hydrocarbon and said olefin.

2. An alkylation process wherein an isoparafiin having from 4 to 8carbon atoms and an olefin having from 2 to 12 carbon atoms arecontacted, in a molar ratio of isoparaflin to olefin between about 2 and50, at a temperature between about 20 C. and 150 C. and a pressurebetween about 100 and 2000 p. s. i., said pressure being at leastsufiicient to keep a substantial portion of said reactants in the liquidstate, for a time sufiicient to permit an appreciable amount ofalkylation reaction to take place, in the presence of a catalystcomprising essentially (i) phosphomolybdic acid containing water ofhydration, and (ii) boron trifluoride, said BF being present in anamount in excess of one mole per mole of hydrate water present in saidacid, removing a product hydrocarbon mixture from said contacting zoneand an alkylate hydrocarbon product is separated from said mixture.

3. The process of claim 2 wherein said isoparafiin is isobutane.

4. The process of claim 2 wherein said isoparaflin is di-isopropyl.

5. The process of claim 2 wherein said olefin is ethylene.

6. The process of claim 2 wherein said olefin is propylene tetramer.

' 7. The process of claim 2 wherein the BF is present in an amount, inexcess of 1 mole per mole of hydrate water, such that the free-3P toolefin weight ratio is between about 0.2 and 1.5.

8. An alkylation process which comprises contacting isobutane andethylene in a molar ratio of isobutane to ethylene between about 2 and25 at a temperature between about 15 C. and 100 C. at a pressure betweenabout 200 and 1000 p. s. i., said pressure being sufiicient to keep asubstantial portion of said reactants in the liquid state for a timesuflicient to permit an appreciable amount of alkylation reaction totake place, in the presence of a catalyst pair comprising essentially(a) a complex consisting of phosphomolybdic acid containing water ofhydration, and about 1 mole of ER per mole of hydrate water present insaid acid and (b) boron trifiuoride in an amount such that the Weightratio of free-BF to ethylene charged is at least about 0.2, removingproduct hydrocarbon mixture containing alkylate product from saidcontacting zone and separating alkylate hydrocarbon product fromunreacted isobutane and ethylene.

9. The process of claim 8 wherein said free-BF /ethylene weight ratio isbetween about 0.35 and 1.

References Cited in the file of this patent UNITED STATES PATENTS2,301,966 Michel et al. Nov. 17, 1942 2,376,119 Bruner et al. May 15,1945 2,390,835 Hennion et al. Dec. 11, 1945 2,425,096 Ipatieif et al.Aug. 5, 1947 2,608,534 Fleck Aug. 26, 1952

1. AN ALKYLATION PROCESS COMPRISING CONTACTING (A) AN ALKYLATABLE FEEDHYDROCARBON FROM THE CLASS CONSISTING OF (1) ISOPARAFFIN HAVING FROM 4TO 8 CARBON ATOMS AND (2) AROMATIC HYDROCARBON AND (B) AN OLEFIN HAVINGFROM 2 TO 12 CARBON ATOMS, IN THE PRESENCE OF A CATALYST COMPRISINGESSENTIALLY (I) PHOSPHOMOLYBDIC ACID CON TAINING WATER OF HYDRATION, AND(II) BF3, SAID BF3 BEING PRESENT IN AN AMOUNT IN EXCESS OF ABOUT 1 MOLEPER MOLE OF WATER OF HYDRATION IN SAID ACID, AT A TEMPERATURE BETWEENABOUT -30*C. AND A TEMPERATURE SUBSTANYTIALLY BELOW THE TEMPERATURE ATWHICH SAID HYDRATE DECOMPOSES, AND AT A PRESSURE SUFFICIENT TO MAINTAINA SUBSTANTIAL PORTION OF SAID REACTANTS IN THE LIQUID STATE, ANDSEPARATING A HYDROCARBON PRODUCT MIXTURE CONTAINING ALKYLATE PRODUCT OFSAID FEED HYDROCARBON AND SAID OLEFIN.